to paraphrase a book I read
'the brits had tea like clockwork, and it didn't matter if Jerry was shooting at them. Same time everyday, no matter what.'
in all seriousness, I actually get why you would have that in a tank. If you have to get out to make it then you risk being fired upon in a more vulnerable state (outside the armored protection of your tank) and therefor a trained tank operator could be killed easily by waiting for him to make tea (or coffee if you were american I guess).